Liquid dispensers for dispensing soaps and other fluids in liquid form are known. In some applications, it is preferable to dispense soaps and alcohol and other fluids in the form of a foam. Generally, as a foam, less soap or alcohol liquid is required to be used as, for example, for proper hand cleaning. As well, soap or alcohol as foam is less likely to run off a user's hands or other surfaces to be cleaned.
The present inventors have appreciated the disadvantage that in many foam pumps, foam is drawn back into the pump, when the pump is left unused for a period of time, the foam which has been drawn back into the pump coalesces, that is, separates into liquid and air with the passage of time. This coalescence of foam within the pump raises a level of liquid in a chamber in the pump. Pumps in which the chamber which the coalescence takes place is open to an outlet, liquid can drip under gravity from the chamber out of the outlet.
The present inventors have also appreciated that in many non-foaming liquid pumps the disadvantage arises that when the pump is left unused for a period of time liquid drips out of the outlet.